Methods for treating migraines with huperzine a derivatives

ABSTRACT

The present invention relates to a method for treating, alleviating, or preventing pain, particularly migraines, functional pain syndrome, or organic pain syndrome, by administering to a patient in need thereof compound (I), or salts thereof, or pharmaceutical preparations thereof comprising mixtures of compound (I) or salts thereof with pharmaceutically-acceptable diluents 
     
       
         
         
             
             
         
       
     
     wherein: R represents —NR 1 R 2 , —NHC(O)OR 3 , or —N═CR 4 R 5 ; R 1  represents H, or a C 1-6  alkyl; R 2  represents H, or a C 1-6  alkyl; R 3  represents a C 1-6  alkyl, a heterocyclic group, or an aryl; R 4  represents H, C 1-6  alkyl, a heterocyclic group or an aryl; and R 5  represents H, C 1-6  alkyl, a heterocyclic group, or an aryl; or CR 4 R 5  taken together represents a cyclolidene group.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/020,520, now pending, which is a National Phase Entry applicationunder 35 U.S.C. 371 of International Patent Application No.PCT/CN2005/001468 with an international filing date of Sep. 13, 2005,designating the United States. This application further claims prioritybenefits to Chinese Patent Application No. 200510014685.6, filed on Aug.1, 2005. The contents of all of the aforementioned specification areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to huperzine A derivatives, and more particularlyto their application in treating or alleviating migraines.

2. Description of the Related Art

Chronic pain types include cancer pain, caused by the tumor pressing onbones, nerves, and other organs; nociceptive pain, caused by damage oftissues or organs; arthritic pain, caused by autoimmune response, suchas inflammation (arthritis, gastritis, hepatitis); and neuropathic pain,especially migraine pain, caused by various abnormalities of the centralnervous system.

Clinically, migraine pain features pulsating headache on one or bothsides of the head, having duration of between 4 and 74 hours for eachattack, and being simultaneously accompanied by symptoms of nausea,vomiting and photophobia. In certain patients specific premonitorysymptoms, lasting about 10 to 20 min, such as visual symptoms of scotomaand light flash, numbness, and dizziness, may occur before the incidenceof migraines.

With acceleration of the life styles and increase of work pressure, theincidence of migraines has been on the rise throughout the world. Infact, migraines constitute now the most common medical conditiondistressing modern people. For example, in China migraine affects 3%-5%of adult population, of which females are more susceptible than males bya factor of 3 to 4. In most cases, the onset of migraine occurs inadolescence.

In developed countries, the incidence of migraine is much higher. Thestatistics from the National Headache Foundation show that one of everyten people suffers from migraine headaches, but more than half of thepatients have not been even properly diagnosed. Similar data from theNational Institute of Neurological Disorders and Stroke has revealedthat there are 28 million patients with migraines in America and thatmigraine has caused an annual loss of about 157 million working days.Not surprisingly, pain management is one of the most common goals ofhomeopathy, and the treatment of migraine has become a hot medicalfield.

Conventional analgesics include two main types: opiate receptor ligands,with the typical example of morphine, which has strong analgesic effectsbut is prone to cause addiction; and non-narcotic analgesics, with thetypical example of aspirin-derived paracetamol. There are also variousnew-age analgesics having multiple mechanisms of action, conceived andmanufactured successfully via modern processes for drug design,screening and development, which have weak analgesic effects, but whichusually do not form dependence. Although some of these analgesics haveserious side effects, e.g., they cause damage to the digestive tract,they are widely used and have an estimated combined market share ofnearly 10 billion US dollars.

In the past twenty years, new types of 5-hydroxytryptamine (5-HT)antagonists and receptor stimulants have been identified in migrainepatophysiology. Meanwhile, the development of analgesics acting onvarious targets of CNS has become a hot field in the new drugdevelopment area. However, most of these research objectives havefocused on the 5-HT receptor and the dopamine receptor. Specifically, inthe last 10 years, it was discovered that the 5-HT receptor and thedopamine receptors are divided into various subtypes, and the ability tointeract with certain subtypes is related to analgesic effects of drugs,as well as the decrease or complete elimination of toxic and other sideeffects. This precipitated a great amount of research on these targets.

Acetylcholine, a neurotransmitter, was discovered much earlier than5-HT. However, the acetylcholine receptor and acetylcholine esterasehave not been popular targets for developing drugs. Nevertheless, inEuropean Pat. No. EP 413667 A and U.S. Pat. No. 5,010,083, compoundsused for treatment of both memory loss and relief of pain have beenreported, which suggests that improvement of memory has some associationwith analgesia, and further reveals that increase in the level ofacetylcholine may have analgesic action.

In addition, Stoyan once reported that the alkaloids nivalin andsyntostigmine may alleviate migraine pain (Stoyan Iv Ikonomoff, ArchivesSuisses de Neurologie, Neurochirurgie et de Psychiatric, Vol. 102,Fascicule, pages 299-312 (1968)). It was later found that these twocompounds may inhibit activity of acetylcholine esterase. Because of alow inhibition activity of acetylcholine esterase or a low ability topermeate the blood-brain barrier, higher doses of these two compounds,and other acetylcholine esterase inhibitors subsequently tested, arerequired in order to provide therapeutic effects.

To achieve high concentrations, these compounds must be administered byinjection. Hence, on one hand, the blood drug concentration is so highso as to have many side effects; on the other hand, the administrationby way of injection is inconvenient. As a result, the research onacetylcholine esterase inhibitors used for treatment of migraine was puton hold. This was the first time when it was proposed that acetylcholineesterase inhibitors could be used for treatment of migraine.

The breakthrough in this field came from research and development ofnovel inhibitors of acetylcholine esterase. These novel inhibitors, suchas donepezil, have high activity, highly-selectivity and easy permeationthrough the blood-brain barrier, so that they are able to overcome theshortcomings of the first generation of acetylcholine esteraseinhibitors described above for the treatment of migraine. As disclosedin U.S. Pat. No. 6,608,088, donepezil was observed to have efficacy inmigraine in clinical trials. But after phase II efficacy studies, theevaluation of the efficacy and safety of donepezil hydrochloride inmigraine prophylaxis was terminated.

The Merck Manual [Migraine, The Merck Manual of Diagnosis and Therapy(17^(th) Edition), pages 1376-1377; 1999] discloses, on page 1376, leftcolumn, paragraphs 4 and 5, wherein the cause of migraines is unknown,and the pathophysiology is not fully understood.

Huperzine A can inhibit acetylcholine esterase selectively, is easy topermeate through the blood-brain barrier, can promote memoryreappearance and enhance memory maintenance. However, no literaturereports have appeared that suggest that huperzine A or its derivativesare useful in the treatment of migraine.

SUMMARY OF THE INVENTION

Promoting function of acetylcholine as a nervous transmitter is areliable new pharmacological mechanism for analgesia. Novel inhibitorsof acetylcholine esterase, with high activity, highly selectiveinhibition of the central acetylcholine esterase, easy permeationthrough the blood-brain barrier, long duration and convenientadministration, provide a breakthrough for pain control, especially fortreatment of migraine.

Through animal experiments, we found that huperzine A and itsderivatives have a much higher efficacy than donepezil. Specifically, wehave found in clinical studies that oral huperzine A alleviates and/orcures migraine, and that long-term administration of huperzine Aprevents migraine attacks.

In certain embodiments of the present invention, provided is a methodfor treating pain, functional pain syndrome or organic pain syndromecomprising administering to a patient in need thereof a compound offormula (I) or the salts thereof to alleviate or treat pain, functionalpain syndrome or organic pain syndrome in mammals,

wherein: R represents —NR¹R², —NHC(O)OR³, —N═CR⁴R⁵; R¹ represents H orC₁₋₆ alkyl; R² represents H or C₁₋₆ alkyl; R³ represents C₁₋₆ alkyl, aheterocyclic group or an aryl; R⁴ represents H, C₁₋₆ alkyl, aheterocyclic group or an aryl; and R⁵ represents H, C₁₋₆ alkyl, aheterocyclic group or an aryl; or CR⁴R⁵ taken together represents acyclolidene group.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for treating, alleviating, orpreventing pain, particularly migraines, functional pain syndrome, ororganic pain syndrome, comprising administering to a patient in needthereof a compound of formula (I), or salts thereof, or pharmaceuticalpreparations thereof comprising mixtures of a compound of formula (I) orsalts thereof with pharmaceutically-acceptable diluents

wherein: R represents —NR¹R², —NHC(O)OR³, —N═CR⁴R⁵; R¹ represents H orC₁₋₆ alkyl; R² represents H or C₁₋₆ alkyl; R³ represents C₁₋₆ alkyl, aheterocyclic group or an aryl; R⁴ represents H, C₁₋₆ alkyl, aheterocyclic group or an aryl; and R⁵ represents H, C₁₋₆ alkyl, aheterocyclic group or an aryl; or CR⁴R⁵ taken together represents acyclolidene group.

When representing C₁₋₆ alkyl, R¹, R², R³, R⁴, or R⁵ may be linear chainalkyl, fork chain alkyl, or cyclic chain alkyl; may be saturated orunsaturated chain alkyl, and may be substituted by one or more fluorine,hydroxyl, alkoxyl, ester group, amidocyanogen, amido, and carboxyl.

When R¹, R², R³, R⁴, or R⁵ represent a heterocyclic group, R¹, R², R³,R⁴, or R⁵ may be a pentacycle, a hexacycle, a heptacycle or anoctocycle; may be saturated or unsaturated cycle; may contain one ormore oxygen, nitrogen or sulfur atoms; and may be substituted by one ormore fluorine, hydroxyl, alkoxyl, ester group, amidocyanogen, amido, orcarboxyl.

When R¹, R², R³, R⁴, or R⁵ represent an aryl group, R¹, R², R³, R⁴, orR⁵ may be a five-membered or a six-membered aryl group; may be a onecycle or a two cycle; may contain one or more than one oxygen, nitrogenor sulfur atoms; and may be substituted by one or more than onefluorine, hydroxyl, alkoxyl, ester group, amidocyanogen, amido, orcarboxyl.

When R represents N═CR⁴R⁵, a compound of formula (I) may be an E-isomer,Z-isomer or mixture of an E-isomer and a Z-isomer.

Among compounds represented by formula (I), suitable as apharmaceutically-active ingredient for the treatment of pain, functionalpain syndrome or organic pain syndrome, are compounds containing R whichrepresents —NR¹R², wherein, R¹, and R² represent independently and ateach occurrence hydrogen, methyl, ethyl, propyl, isopropyl or butyl;particularly suitable as a pharmaceutically active ingredient fortreatment of pain, functional pain syndrome or organic pain syndrome,are compounds containing R which represents —NR¹R², wherein, R¹, and R²represent independently and at each occurrence hydrogen, methyl, ethyl,or propyl; and most particularly suitable as a pharmaceutically activeingredient for treatment of pain, functional pain syndrome or organicpain syndrome, are compounds containing R which represents NR¹R²,wherein, R¹, and R² represent hydrogen, or methyl.

Among compounds represented by formula (I), suitable as apharmaceutically active ingredient for treatment of pain, functionalpain syndrome or organic pain syndrome, are compounds containing R whichrepresents —NHC(O)OR³, wherein, R³ represents independently and at eachoccurrence methyl, ethyl, propyl, isopropyl, butyl, isobutyl,tert-butyl, neo-butyl, 1-pentyl, 1-methylbutyl, 2-methylbutyl,3-methylbutyl, 1,1,-dimethylpropyl, 2,2-dimethylpropyl,1,2-dimethylpropyl, cyclopentyl, cyclohexyl, hexyl, phenyl, 2-Cl-phenyl,3-Cl-phenyl, 4-Cl-phenyl, 2-OH-phenyl, 3-OH-phenyl, 4-OH-phenyl,2-aminophenyl, 3-aminophenyl, 4-aminophenyl, 2-methylaminophenyl,3-methylaminophenyl, 4-methylaminophenyl, 2-methylphenyl,3-methylphenyl, 4-methylphenyl, 2-methoxylphenyl, 3-methoxylphenyl,4-methoxylphenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl,2-pyridyl, 3-pyridyl, 4-pyridyl, or phenylmethyl; particularly suitableas a pharmaceutically active ingredient for treatment of pain,functional pain syndrome or organic pain syndrome, are compoundscontaining R which represents —NHC(O)OR³, wherein, R³ represent methyl,ethyl, propyl isopropyl, butyl, tert-butyl, phenyl, 2-Cl-phenyl,3-Cl-phenyl, 4-Cl-phenyl, 2-OH-phenyl, 3-OH-phenyl, 4-OH-phenyl,2-methylaminophenyl, 3-methylaminophenyl, 4-methylaminophenyl,2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-methoxylphenyl,3-methoxylphenyl, 4-methoxylphenyl, 2-fluorophenyl, 3-fluorophenyl,4-fluorophenyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, or phenylmethyl; andmost particularly suitable as a pharmaceutically active ingredient fortreatment of pain, functional pain syndrome or organic pain syndrome,are compounds containing R which represents —NHC(O)OR³, wherein, R³represent ethyl, propyl, isopropyl, butyl, tert-butyl, phenyl, orphenylmethyl.

Among compounds represented by formula (I), suitable as apharmaceutically active ingredient for treatment of pain, functionalpain syndrome or organic pain syndrome, are compounds containing R whichrepresents —N═CR⁴R⁵, wherein, R⁴, R⁵ represent independently and at eachoccurrence hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl,tert-butyl, neo-butyl, 1-pentyl, 1-methylbutyl, 2-methylbutyl,3-methylbutyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl,1,2-dimethylpropyl, cyclopentyl, cyclohexyl, hexyl, phenyl, 2-Cl-phenyl,3-Cl-phenyl, 4-Cl-phenyl, 2-OH-phenyl, 3-OH-phenyl, 4-OH-phenyl,3,4-dihydroxylphenyl, 3-OH-4-(C₁₋₅-alkyloxyl)phenyl,3-(C₁₋₅-alkyloxyl)-4-(C₁₋₅-alkyloxyl)phenyl, 2-aminophenyl,3-aminophenyl, 4-aminophenyl, 2-methylaminophenyl, 3-methylaminophenyl,4-methylaminophenyl, 2-dimethylaminophenyl, 3-dimethylaminophenyl,4-dimethylaminophenyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl,2-methoxylphenyl, 3-methoxylphenyl, 4-methoxylphenyl, 2-fluorophenyl,3-fluorophenyl, 4-fluorophenyl, 2-thienyl, 3-thienyl, 2-furanyl,3-furanyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, or phenylmethyl;particularly suitable as a pharmaceutically active ingredient fortreatment of pain, functional pain syndrome or organic pain syndrome,are compounds containing R which represents —N═CR⁴R⁵, wherein, R⁴, andR⁵ represent independently and at each occurrence hydrogen, methyl,ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, neo-butyl,cyclopentyl, cyclohexyl, hexyl, phenyl, 2-Cl-phenyl, 3-Cl-phenyl,4-Cl-phenyl, 2-OH-phenyl, 3-OH-phenyl, 4-OH-phenyl,3,4-dihydroxylphenyl, 3-OH-4-methoxylphenyl,3-methoxyl-4-methoxylphenyl, 2-methylphenyl, 3-methylphenyl,4-methylphenyl, 2-methoxylphenyl, 3-methoxylphenyl, 4-methoxylphenyl,2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2-pyridyl, 3-pyridyl, or4-pyridyl; and most particularly suitable as a pharmaceutically activeingredient for treatment of pain, functional pain syndrome or organicpain syndrome, are compounds containing R which represents —N═CR⁴R⁵,wherein, R⁴, and R⁵, represent independently and at each occurrencehydrogen, methyl, ethyl, propyl, isopropyl, butyl, cyclohexyl, phenyl,3-OH-4-methoxylphenyl, 3-hydroxylphenyl, 4-methoxylphenyl,3-fluorophenyl, or 4-pyridyl.

The compounds represented by formula (I) to be used for treatment ofpain, functional pain syndrome or organic pain syndrome, and variouspharmaceutically-acceptable inorganic acid salts or organic acid saltsthereof are administered at a dose of between 0.001 and 500 mg peradministration; more particularly, at a dose of between 0.01 and 100 mgper administration, and most particularly at a dose of between 0.05 and50 mg per administration. Single or multiple daily administrations maybe necessary. Particularly, the compound may be administered once,twice, three times, or four times per day, or at a different dosinginterval, e.g., as ordered by a physician.

This invention relates also to pharmaceutical compositions comprising acompound represented by formula (I), and a carrier, filler, solvent,diluter, colorant, and/or adhesive. The proportion of the compoundrepresented by formula (I) to a carrier, filler, solvent, diluter,colorant, and/or adhesive depends on the mode of administration. Modesof administration include those through the gastrointestinal tract, theoral cavity, the vein, the endodermis, the muscle injection, the nasalcavity, the eye, inhalation, the anus, the vaginal tract, thepercutaneous absorption, and other ways.

The pharmaceutical composition of the present invention may also beprepared as a control-release agent.

The pharmaceutical composition of the present invention may alsocomprise other pharmaceutically-active ingredients, including e.g.,other pharmaceutically-active ingredients used heretofor to alleviatepain, including migraines.

The pain meant to be treated, alleviated, or prevented by compounds andmethods of the present invention includes all distress resulting frompain, functional pain syndrome, or organic pain syndrome, including butnot limited to nervous headache, especially migraine, primaryfibromylgia, amputation resulting from fracture trauma, tumoraldenervation resulting from damage to nerves caused by tumor, traumaticdenervation resulting from nervous injury, or pain resulting frompathological damage of autoimmune mechanism.

EXAMPLES Example 1

(5R,9R,11E)-5-amino-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one(Huperzine A), was purchased from the Institute of Poison and Drug,Chinese Academy of Military Medical Sciences.

Example 2

(5R,9R,11E)-5-methylamino-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

Huperzine A 10 mg, and 37% aqueous solution of formaldehyde wererefluxed for 1 hour in 2 mL of isopropanol; the solvent was stripped invacuo; THF (dry, 5 mL) and NaBH(OOCCH₃)₃ 0.15 g were added, the reactionmixture was allowed to stir for 4 hours; and then filtered to removesolid substances. The filtrate was purified after concentrating on prepTLC (chloroform:methanol=9:1) to yield 6 mg of pure title compound. MS:257 (M+1).

Example 3

(5R,9R,11E)-5-dimethylamino-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 2, except thathuperzine A was replaced with(5R,9R,11E)-5-dimethylamino-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one.MS: 271(M+1).

Example 4

(5R,9R,11E)-5-ethylamino-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 2, except thatformaldehyde was replaced with acetaldehyde. MS: 271(M+1).

Example 5

(5R,9R,11E)-5-butylamino-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 2, except thatformaldehyde was replaced with butyraldehyde. MS: 299(M+1).

Example 6

(5R,9R,11E)-5-(ethoxycarbonylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

Dissolved 10 mg huperzine A and 10 mg triethylamine in 5 mL dry THF;cooled the solution down to 0° C.; added ethyl chlorocarbonate (6 mg)and stirred the resultant reaction mixture for 4 hours; filtered toremove solid residues; after concentrating the filtrate, purified onprep TLC (chloroform:methanol=9:1) to yield 8 mg of pure title compound.MS: 315(M+1).

Example 7

(5R,9R,11E)-5-(2-methylpropoxycarbonylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 6, except thatethyl chlorocarbonate was replaced with isobutyl chlorocarbonate.

Example 8

(5R,9R,11E)-5-(Cert-butoxycarbonylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 6, except thatethyl chlorocarbonate was replaced with tert-butyl chlorocarbonate.

Example 9

(5R,9R,11E)-5-(benzyloxycarbonylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 6, except thatethyl chlorocarbonate was replaced with methyl benzyl chlorocarbonate.

Example 10

(5R,9R,11E)-5-(4-hydroxy-3-methoxyphenylmethylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

Added 10 mg huperzine A and 8 mg vanillin in 5 mL isopropanol; stirredat reflux for 3 hours; stripped solvent in vacuo to yield 16 mg product.MS: 377(M+1).

Example 11

(5R,9R,11E)-5-(3-hydroxy-4-methoxyphenylmethylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 10, except thatvanillin was replaced with isovanillin. MS: 377(M+1).

Example 12

(5R,9R,11E)-5-phenylmethylidenylamino-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 10, except thatvanillin was replaced with benzaldehyde. MS: 331(M+1).

Example 13

(5R,9R,11E)-5-(4-pyridinylmethylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 10, except thatvanillin was replaced with 4-pyridylaldehyde. MS: 332(M+1).

Example 14

(5R,9R,11E)-5-(cyclohexanylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 10, except thatvanillin was replaced with cyclohexanone. MS: 323(M+1).

Example 15

(5R,9R,11E)-5-(1-methylpiperidin-4-ylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 10, except thatvanillin was replaced with 1-methyl-4-piperidone. MS: 338(M+1).

Example 16

(5R,9R,11E)-5-(cyclohexanylmethylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 10, except thatvanillin was replaced with cyclohexylaldehyde.

Example 17

(5R,9R,11E)-5-(2-butylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 10, except thatvanillin was replaced with butanone.

Example 18

(5R,9R,11E)-5-(1-butylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one

The title compound was prepared as described in Example 10, except thatvanillin was replaced with butyraldehyde.

Example 19

(5R,9R,11E)-5-(4-methoxyphenylmethylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 10, except thatvanillin was replaced with 4-methoxybenzaldehyde. MS: 361 (M+1).

Example 20

(5R,9R,11E)-5-(3-hydroxyphenylmethylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 10, except thatvanillin was replaced with 3-hydroxybenzaldehyde. MS: 347 (M+1).

Example 21

(5R,9R,11E)-5-(3-fluorophenylmethylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one:

The title compound was prepared as described in Example 10, except thatvanillin was replaced with 3-fluorobenzaldehyde. MS: 349 (M+1).

Animal Tests Test 1 Hot Plate Test

1. Test Materials

1.1 Animals

Kunming mice, grade 2, female, weight of 20±2 g, purchased from theDivision of Laboratory Animals, Department of Medical Sciences of PekingUniversity, animal license No.: SCX Jing 2002-0001.

1.2 Drugs

1.2.1 Solutions of huperzine A and huperzine A derivatives in normalsaline water were prepared for stomach perfusion of mice.

1.2.2 Solutions of bucinnazine hydrochloride tablets, 30 mg/tablet,manufactured by Tianjin Lisheng Pharmaceutical Factory, approval No.:0201001, in normal saline solution were prepared at a concentration of1.5 mg/ml for stomach perfusion of mice.

2. Methods

A water bath was heated to a constant temperature of 55±0.5° C. Thebottom of a metal plate was placed in contact with water surface. Amouse was placed on the hot plate and a timer was activated. The timerwas deactivated when the mouse began licking its rear feet. The measuredtime was taken as the pain threshold. The pain threshold was measuredtwo times for each mouse, and those mice whose average pain thresholdwas less than 30 s were qualified for the experiment.

Qualified mice were randomly divided into groups of 10. At first thepain threshold before administration of a drug was measured. Then drugswere administered as identified in Table 1. The administration volumewas 0.2 ml per each 10 g of weight. Normal saline solution wasadministered to the control group. After administration, the painthreshold was measured at different time periods post-administration. Astatistical t-test was calculated of the group interval, based on thetest data.

3. Results

The results are shown as Table 1.

TABLE 1 Effect of drugs on the pain thresholds for mice in a hot platetest (x ± s, n = 10) Pain thresholds before Pain Thresholds in DifferentPeriods Dose administration after Administration(s) Groups mg/kg (s) at30 min at 60 min at 120 min at 180 min at 240 min Control — 16.2 ± 2.7913.7 ± 3.53 14.8 ± 4.41 14.5 ± 3.27 14.7 ± 2.98 14.7 ± 2.71 Huperzine A0.2 14.2 ± 4.49 13.3 ± 4.05 14.5 ± 5.08 14.2 ± 5.20 13.3 ± 3.68 14.6 ±2.84 Huperzine A 0.4 15.3 ± 2.86 28.4 ± 8.12*** 31.7 ± 10.56*** 27.6 ±8.22*** 25.5 ± 8.88** 27.8 ± 5.94*** Compound of 0.6 15.8 ± 3.97 28.5 ±2.55** 30.1 ± 6.90*** 27.7 ± 4.49*** 23.1 ± 2.41** Example 7 Compound of0.6 16.9 ± 2.77 26.2 ± 5.94** 32.8 ± 7.36*** 29.6 ± 6.60*** 25.8 ±1.84** Example 10 Notes: By comparing with the control group, *p < 0.05;**p < 0.01; ***p < 0.001

Test 2 Treatment of Migraine with Oral Huperzine A

Drug: Huperzine A Tablet (50 μg/tablet, manufactured by Henan Zhulin

Zhongsheng Pharmaceutical Factory.)

Case 1:

Patient: Female, 38-year old, with a medical history of migraine of 5years, exhibiting nausea during attacks of migraine, and occasionallyvomiting. Previously treated with bufferin plus, but recently reportedthat analgesic effects of bufferin plus have weakened.

Methods: On occurrence of migraine pains (8 times within a month), twotablets of huperzine A were administered. Within 20 minutes fromadministration, the headache has completely disappeared. Minor sideeffects were observed. Good analgesic effects were reported over aperiod of one month.

Case 2:

Patient: Female, 41-year old, with a medical history of migraine of 2years. Previously treated with ergotamine, but recently reported thatanalgesic effects of ergotamine have weakened.

Methods: On occurrence of migraine pains (10 times within a month), twotablets of huperzine A were administered. Within 30 minutes fromadministration, the headache has completely disappeared. No side effectswere observed. Good analgesic effects were reported over a period of onemonth.

Case 3:

Patient: Female, 41-year old, with a medical history of migraine of 3years, occurring at a frequency of about 8-12 times per month.

Methods: One tablet of huperzine A was administered per day orally. Thepatient did not complain of migraine attacks over the period of 1 month.

Test 3 The Preventive Effect of Huperzine A on Nitroglycerin-inducedMigraine Mice Model

1. Animals

Adult female KunMing mice (weight 22-27 g) were housed in plastic boxesin groups of 5, with water and food provided ad libitum. They were kepton a 12 h/12 h light-dark cycle and acclimatized to the test chamberbefore testing, animal license No.: SCXK June 2006-004.

2. Experimental Protocols and Groups

Mice were divided into 6 groups (12 each). Doses of 0.02, 0.06, 0.18mg/kg (20 ml/kg) Huperzine A, 4.50 mg/kg (20 ml/kg) flunarizinehydrochloride or 24 mg/kg (20 ml/kg) Tacrine were administered orally(intragastric administration). Normal group and vehicle group receiveddistilled water. Animals were given nitroglycerin or 0.9% saline (normalgroup) after 0.5 h. Nitroglycerin was injected subcutaneously (s.c.) onthe back at the dose of 10 mg/kg (10 ml/kg).

Thereafter, the number of head-scratching in every 30 min was recordedfor 1.5 h after nitroglycerin injection.

The inhibition of the number of head-scratching=(The number ofhead-scratching of Vehicle−The number of head-scratching ofTreatment)/(The number of head-scratching of Vehicle−The number ofhead-scratching of Normal).

3. Results

The results are shown as Tables 2 and 3.

TABLE 2 The number of head-scratching in every 30 min (Mean ± S.E.)Group 0-30 min 30-60 min 60-90 min Normal 9.4 ± 2.2  7.4 ± 1.2  5.8 ±2.3  Vehicle   55.3 ± 11.9**  43.8 ± 6.6**  37.9 ± 8.6** Tacrine-24mg/kg 50.5 ± 7.5   45.5 ± 5.7   35.6 ± 7.8   Flunarizinehydrochloride-4.50 mg/kg 24.1 ± 4.7^(ΔΔ) 17.8 ± 3.2^(ΔΔ) 13.9 ± 4.0^(ΔΔ)Huperzine A -0.18 mg/kg 12.4 ± 3.3^(ΔΔ) 25.4 ± 4.6^(ΔΔ) 25.0 ± 5.8  Huperzine A -0.06 mg/kg 28.8 ± 5.7^(ΔΔ) 24.3 ± 5.8^(ΔΔ) 14.3 ± 3.3^(ΔΔ)Huperzine A -0.02 mg/kg  36.3 ± 5.0^(Δ▴) 21.4 ± 3.2^(ΔΔ) 17.5 ± 5.3^(ΔΔ)Compared with normal, **P < 0.01; Compared with vehicle, ^(Δ)P < 0.05,^(ΔΔ)P < 0.01; Compared with Huperzine A -0.18 mg/kg, ^(▴)P < 0.05.

TABLE 3 The inhibition of Huperzine A on the number of head-scratching(%) Group 0-30 min 30-60 min 60-90 min Tacrine-24 mg/kg 10.4 −4.7 7.2Flunarizine hydrochloride-4.50 mg/kg 68.0 71.4 74.6 Huperzine A -0.18mg/kg 93.5 50.6 40.2 Huperzine A -0.06 mg/kg 57.8 53.5 73.3 Huperzine A-0.02 mg/kg 41.3 61.6 63.5

This assay proved the preventive effect of Huperzine A onnitroglycerin-induced migraine mice model. In this model, the number ofhead-scratching was used as a read-out for it reflected migraineseverity. With the dose of 0.02, 0.06, 0.18 mg/kg, Huperzine A reducedthe number of head-scratching significantly. And the effect wasdose-dependent, especially in the 0-30 min interval.

1. A method for treating or alleviating migraines comprisingadministering to a patient in need thereof a compound of the formula(I), or its salt,

wherein R represents —NR¹R²; R¹ represents H, or a C₁₋₆ alkyl; and R²represents H, or a C₁₋₆ alkyl;
 2. The method of claim 1, wherein Rrepresents —NR¹R²; and R¹ and R² represent independently and at eachoccurrence hydrogen or a C₁₋₃ alkyl.
 3. The method of claim 1, wherein Rrepresents —NR¹R²; and R¹ and R² represent independently and at eachoccurrence hydrogen, methyl, or ethyl.
 4. The method of claim 1, whereinthe compound of the general formula (I), or its salt is administered tothe patient by a mode of administration selected from gastrointestinal,oral, intravenous, abdominal, dermal, intramuscular, nasal, ocular,pulmonary, anal, vaginal, or transdermal.
 5. The method of claim 1,wherein the compound of the general formula (I), or its salt isadministered to the patient at a dose of between 10 μg and 100 mg.
 6. Amethod for treating or alleviating migraines comprising administering toa patient in need thereof a compound of formula (I), or its salt,

wherein R represents —NR¹R²; R¹ represents H, or a C₁₋₆ alkyl; R²represents H, or a C₁₋₆ alkyl; and except that R¹ and R² are notsimultaneously H.
 7. A method for treating or alleviating migrainescomprising administering to a patient in need thereof a compound of theformula (I), or its salt,

wherein R represents —NHC(O)OR³, or —N═CR⁴R⁵; R³ represents a C₁₋₆alkyl, a heterocyclic group, or an aryl; and R⁴ and R⁵ representindependently a C₁₋₆ alkyl, a heterocyclic group, or an aryl; or CR⁴R⁵taken together represents a cyclolidene group.
 8. The method of claim 7,wherein R represents —N═CR⁴R⁵; and CR⁴R⁵ represent cyclopentylidene,cyclohexylidene, or 1-methyl-4-piperidinylidene.
 9. The method of claim7, wherein R represents —N═CR⁴R⁵; and R⁴ and R⁵ represent, independentlyand at each occurrence, hydrogen, a C₁₋₃ alkyl, a phenyl, a substitutedphenyl, a 2-pyrrolinyl, a 3-pyridinyl, or a 4-pyridinyl.
 10. The methodof claim 7, wherein the compound of the general formula (I), or its saltis administered to the patient by a mode of administration selected fromgastrointestinal, oral, intravenous, abdominal, dermal, intramuscular,nasal, ocular, pulmonary, anal, vaginal, or transdermal.
 11. The methodof claim 7, wherein the compound of the general formula (I), or its saltis administered to the patient at a dose of between 10 μg and 100 mg.12. The method of claim 7, wherein said compound of formula (I) is(5R,9R,11E)-5-(2-methylpropoxycarbonylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one.13. The method of claim 7, wherein said compound of formula (I) is(5R,9R,11E)-5-(4-hydroxy-3-methoxyphenylmethylidenylamino)-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one.